Shoulder Prosthetic

ABSTRACT

A shoulder implant assembly including a humeral stem, a head, a cup, and a taper adaptor. The humeral stem is configured to be inserted into a humerus bone. The head includes a metal substrate having a coupling taper and a polymeric cover mounted to the metal substrate having a convex outer surface and a generally planar base. The cup has a concave surface configured to articulate with the polymeric cover of the head. The taper adaptor is configured to mate with the coupling taper of the head. The taper adaptor is configured to connect the head to the stem when the cup is connected to a glenoid. The taper adaptor is configured to connect the head to the glenoid when the cup is connected to the humeral stem.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.13/473,749 filed on May 17, 2012, which is a continuation of U.S. patentapplication Ser. No. 12/620,834 filed on Nov. 18, 2009, issued as U.S.Pat. No. 8,246,687. The entire disclosures of the above applications areincorporated herein by reference.

FIELD

The present disclosure relates to an implant for shoulder jointreplacement.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

A natural shoulder joint may undergo degenerative changes for a varietyof different reasons. When these degenerative changes become advancedand irreversible, it may become necessary to replace a natural shoulderjoint with a prosthetic shoulder joint.

Shoulder joint implants often include a humeral component and a glenoidcomponent. The humeral component generally includes a stem, a head, andan adaptor for coupling the head with the stem. The head is often madeof metal, such as cobalt-chrome. The glenoid component is generallymodular and includes a metal tray and a bearing mounted thereto. Thebearing includes an articulating surface that receives and articulateswith the head. The bearing is often made out of an ultra-high molecularweight polyethylene (“UHMWPE”) material.

While such shoulder implants are suitable for their intended use, itwould be desirable to provide a shoulder implant having a reduced weightto decrease the amount of stress that is typically transferred throughthe implant to the bone and/or soft tissue. Further, it would bedesirable to provide a shoulder implant that permits less bone to beresected during implantation, reduces wear between the components,enhances fixation of the glenoid component, and facilitatespostoperative procedures.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

The present teachings provide for a shoulder implant assembly includinga humeral stem, a head, a cup, and a taper adaptor. The humeral stem isconfigured to be inserted into a humerus bone. The head includes a metalsubstrate having a coupling taper and a polymeric cover mounted to themetal substrate having a convex outer surface and a generally planarbase. The cup has a concave surface configured to articulate with thepolymeric cover of the head. The taper adaptor is configured to matewith the coupling taper of the head. The taper adaptor is configured toconnect the head to the stem when the cup is connected to a glenoid. Thetaper adaptor is configured to connect the head to the glenoid when thecup is connected to the humeral stem.

The present teachings further provide for a shoulder implant assemblyincluding a humeral stem, a polymeric head, a cup, and a taper adaptor.The humeral stem is configured to be inserted into a humerus bone. Thepolymeric head includes a convex outer surface, a polymeric couplingtaper, and a generally planar base. The cup has a concave surfaceconfigured to articulate with the polymeric head. The taper adaptor isconfigured to mate with the polymeric coupling taper of the head. Thetaper adaptor is configured to connect the head to the stem when the cupis connected to a glenoid. The taper adaptor is configured to connectthe head to the glenoid when the cup is connected to the humeral stem.

The present teachings also provide for a head for a shoulder implantassembly that includes a polymeric cover and a metal substrate. Thepolymeric cover includes a convex outer surface and a generally planarbase. The metal substrate has the polymeric cover mounted thereto. Themetal substrate includes a coupling taper, a retention flange to securethe polymeric cover to the metal substrate, and an anti-rotation tab toprevent the polymeric cover from rotating about the metal substrate.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is an exploded view of a shoulder implant assembly in accordancewith various embodiments of the present teachings;

FIG. 2A is a cross-sectional view of the implant assembly of FIG. 1illustrating the interaction between different components of theassembly;

FIG. 2B is a cross-sectional view of an implant assembly according toanother aspect of the present teachings;

FIG. 3A is a perspective view of a head of the implant assembly of FIG.1;

FIG. 3B is a cross-sectional view of FIG. 3A taken along line 3B-3B ofFIG. 3A;

FIG. 3C is a top view of the head of FIG. 3A;

FIG. 4 is a cross-sectional view of an implant assembly according to afurther aspect of the present teachings;

FIG. 5A is a side view of an offset implant assembly according to thepresent teachings with a head of the assembly at a first position;

FIG. 5B is a side view of the implant assembly of FIG. 5A with the headat a second position;

FIG. 6A is a perspective view of a head substrate according to thepresent teachings;

FIG. 6B is a side view of the substrate of FIG. 6A;

FIG. 6C is a top view of the substrate of FIG. 6A;

FIG. 7A is a perspective view of a head substrate according toadditional aspects of the present teachings;

FIG. 7B is a side view of the substrate of FIG. 7A;

FIG. 7C is a top view of the substrate of FIG. 7A;

FIG. 8A is a perspective view of a head substrate according to furtheraspects of the present teachings;

FIG. 8B is a side view of the substrate of FIG. 8A;

FIG. 8C is a top view of the substrate of FIG. 8A;

FIG. 9A is a perspective view of a head substrate according toadditional aspects of the present teachings;

FIG. 9B is a side view of the substrate of FIG. 9A;

FIG. 9C is a top view of the substrate of FIG. 9A;

FIG. 10A is a perspective view of a head substrate according to furtheraspects of the present teachings;

FIG. 10B is a side view of the substrate of FIG. 10A;

FIG. 10C is a top view of the substrate of FIG. 10A;

FIG. 11A is a cross-sectional view of an additional head according tothe present teachings;

FIG. 11B is a cross-sectional view of a head according to furtheraspects of the present teachings;

FIG. 12A is a side-view of a head according to the present teachings;and

FIG. 12B is a cross-sectional view of a head according to furtheraspects of the present teachings.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

Example embodiments are provided so that this disclosure will bethorough, and will fully convey the scope to those who are skilled inthe art. Numerous specific details are set forth such as examples ofspecific components, devices, and methods, to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to those skilled in the art that specific details need not beemployed, that example embodiments may be embodied in many differentforms and that neither should be construed to limit the scope of thedisclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail.

Although the terms first, second, third, etc. may be used herein todescribe various elements, components, regions, layers and/or sections,these elements, components, regions, layers and/or sections should notbe limited by these terms. These terms may be only used to distinguishone element, component, region, layer or section from another region,layer or section. Terms such as “first,” “second,” and other numericalterms when used herein do not imply a sequence or order unless clearlyindicated by the context. Thus, a first element, component, region,layer or section discussed below could be termed a second element,component, region, layer or section without departing from the teachingsof the example embodiments.

Spatially relative terms, such as “inner,” “outer,” “beneath”, “below”,“lower”, “above”, “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms may be intended to encompass different orientations ofthe device in use or operation in addition to the orientation depictedin the figures. For example, if the device in the figures is turnedover, elements described as “below” or “beneath” other elements orfeatures would then be oriented “above” the other elements or features.Thus, the example term “below” can encompass both an orientation ofabove and below. The device may be otherwise oriented (rotated 90degrees or at other orientations) and the spatially relative descriptorsused herein interpreted accordingly.

With initial reference to FIG. 1, a shoulder implant assembly accordingto various embodiments of the present teachings is illustrated atreference numeral 10. While the present invention is described hereinwith reference to a shoulder implant assembly, one skilled in the artwill recognize that the invention is equally applicable to a variety ofother implants as well, such as any suitable implant configured toreplace what is commonly referred to in the art as a ball-in-socketjoint, including a hip replacement implant.

The implant assembly 10 generally includes a humeral stem 12, a cup 14,a taper adaptor 16, and a head 18.

The humeral stem 12 includes a proximal end 20 and a distal end 22. Theproximal end 20 includes a female taper 24 configured to receive thetaper adaptor 16. The distal end 22 is at the end of an elongatedportion 26 that is configured to be received in a humerus bone 28. Thehumeral stem 12 can be made of any suitable biocompatible material, suchas cobalt-chrome and/or titanium.

With additional reference to FIGS. 2A and 2B, the cup 14 includes aunitary base 29 having a convex articulating surface 30 formed therein.Extending from a side of the base 24 that is opposite to the convexarticulating surface 30 are one or more mounting posts 32. The mountingposts 32 can take the form of any suitable mounting or connectingdevice, such as a fixation peg or screw, suitable to secure the cup 14to a glenoid cavity 34. The mounting posts 32 can be unitary with thebase 29 or modular. The cup 14 can be made of any suitable material,including metals (FIG. 2A) and polymers (FIG. 2B). Suitable metalsinclude cobalt chrome and/or titanium. Suitable polymers includeultra-high molecular weight polyethylene, polyether ether ketone(“PEEK”), carbon fiber reinforced PEEK (such as PEEK-OPTIMA® fromInvibio, Ltd. of the United Kingdom), and/or vitamin E stabilized highlycrosslinked polyethylene (HXLPE), such as is disclosed in U.S. Pat. No.7,431,874. U.S. Pat. No. 7,431,874 is incorporated by reference herein,as well as are all patent applications and issued patents that relythereon for priority including the following U.S. patent applicationSer. No. 11/104,580 filed on Apr. 13, 2005; Ser. No. 11/104,582 filed onApr. 13, 2005; Ser. No. 11/564,594 filed on Nov. 29, 2006; Ser. No.11/948,393 filed on Nov. 30, 2007; and Ser. No. 12/464,235 filed on May12, 2009. An exemplary vitamin E stabilized HXLPE that may be usedincludes E1™ Antioxidant Infused Technology offered by BiometOrthopedics, Inc. of Warsaw, Ind.

The taper adaptor 16 generally includes a first male taper 36 and asecond male taper 38. The first and the second male tapers 36 and 38 areeach generally cylindrical. The first male taper 36 has a largerdiameter than the second male taper 38. The first male taper 36 isangled to cooperate with a corresponding taper of the head 18, asfurther described herein. The second male taper 38 is angled tocooperate with the female taper 24 of the humeral stem 12 to create aMorse taper lock between the taper adaptor 16 and the humeral stem 12.The taper adaptor 16 can be made of any suitable material, such ascobalt chrome and/or titanium.

With additional reference to FIGS. 3A-3C, the head 18 generally includesa metallic substrate 40 and a polymeric cover 42. The metallic substrate40 can be made from any suitable metal, including cobalt-chrome and/ortitanium. The metallic substrate 40 includes a coupling taper 44 havingangled sidewalls 46. The sidewalls 46 are angled to receive the firstmale taper 36 of the taper adaptor 16 to connect the head 18 to thetaper adaptor 16 with a Morse taper. The sidewalls 46 extend from a base48 of the metallic substrate 40.

The base 48 generally includes a retention feature to secure thepolymeric cover 42 to the substrate 40 and an anti-rotation feature toprevent the cover 42 from rotating about the substrate 40. Asillustrated, the retention feature includes a flange 50 and theanti-rotation feature includes tabs 52. The base 48 is illustrated toinclude four tabs 52, but any suitable number of tabs can be provided,as well as any irregular, non-circular surface.

The polymeric cover 42 includes a concave outer surface 54, a generallyplanar base surface 56, and a generally circular opening 58 defined bythe base surface 56. The polymeric cover 42 sits atop the base 48 of themetallic substrate 40 and extends around the flange 50 of the base 48.The flange 50 prevents the polymeric cover 42 from separating from thesubstrate 40. The tabs 52 prevent the polymeric cover 42 from rotatingabout the substrate 40.

The polymeric cover 42 can be made of any suitable biocompatiblematerial, such as polyether ether ketone (“PEEK”) and/or carbon fiberreinforced PEEK. For example, carbon fiber reinforced PEEK-OPTIMA® fromInvibio, Ltd. of the United Kingdom can be used. The polymeric cover 42can also include vitamin E stabilized (HXLPE). An exemplary vitamin Estabilized HXLPE that may be used includes E1™ Antioxidant InfusedTechnology offered by Biomet Orthopedics, Inc. of Warsaw, Ind.

The polymeric cover 42 can be mounted to the substrate 40 in anysuitable matter. For example, the polymeric cover 42 can be injectionmolded over the substrate 40 such that the cover 42 extends around theflange 50. The polymeric cover 42 and the substrate 40 can be finishedbefore or after the molding process. For example, the polymeric cover 42without the concave outer surface 54 can be molded over the substrate 40with the coupling taper 44 not yet formed therein. The coupling taper 44can subsequently be machined in the substrate 40 and the concave outersurface 54 can be machined in the cover 42. To machine the couplingtaper 44, the head 18 can be supported by the unmachined cover 42, whichis often in the form of a blank block of PEEK or HXLPE for example, orsupport features provided in unmachined cover 42, such as chuckingstubs. To machine the concave outer surface 54, the head 18 can besupported at the coupling taper 44. The concave outer surface 54 isshaped to permit articulation with the convex articulating surface ofthe cup 14.

The height of the head 18 can be customized as necessary for differentpatients. For example, if a lower, or flatter, head is desirable, lesspolymeric material can be used over the substrate 40 and/or the base 48of the substrate 40 can be made thinner. Conversely, if a higher or morerounded head is desirable, additional polymeric material can be usedover the substrate 40 and/or the base 48 can be made thicker.

Thus, with renewed reference to FIG. 1, the implant assembly 10 isoperable to replace an anatomical shoulder joint. The polymeric cover 42provides the head 18 with a reduced weight as compared to heads that areentirely made of metal. The reduced weight decreases the amount ofstress that is typically transferred through the implant to thesurrounding bones and/or soft tissue. Further, the metallic cup 14 ofFIG. 2A can be made generally thinner than a modular polymeric cup,thereby reducing the amount of bone that is typically resected at theglenoid cavity 34. This allows more bone stock to be retained to enhancefixation and facilitate post-operative revision surgery. Also, with ametallic cup 14, the surface area of the cup 14 can be provided with anincreased porous portion to enhance bone in-growth.

One skilled in the art will recognize that providing the head 18 with apolymeric cover 42 is applicable to a variety of other applications, asis the metallic cup 14. For example and with additional reference toFIG. 4, the head 18 can be used in a reverse shoulder implant assembly60. With the reverse shoulder implant assembly 60, the cup 14 is mountedto the humeral stem 12 with a taper connection between a male taper 62of the cup 14 and the female taper 24 of the humeral stem 12. The head18 is mounted in the glenoid cavity 34 (illustrated in FIG. 1) with amounting stem 64. The mounting stem 64 includes a male taper 66 that issized to mate with the coupling taper 44 of the head 18 and an elongatedportion 68 that can be implanted directly in the glenoid cavity 34 ormounted to an intermediate mounting device that is mounted in theglenoid cavity 34.

With additional reference to FIGS. 5A and 5B, the head 18 can also beoffset in order to provide for a more accurate reproduction of thenatural anatomy. When the head 18 is offset, an axis A of the circularopening 58 in the base 48, as well as the coupling taper 44, is offsetfrom an axis B of the polymeric cover 42 and the overall head 18.Further, the first male taper 36 of the taper adaptor 16 can be offsetfrom the second male taper 38. By rotating the taper adaptor 16 and/orthe head 18, the head 18 can be moved to a desired offset position, suchas from position A′ (FIG. 5A) to offset position B′ (FIG. 5B), as isprovided for in the Versa-Dial® glenosphere and humeral head sold byBiomet of Warsaw, Ind. and disclosed in U.S. patent application Ser. No.11/357,794 and related applications, which are incorporated herein byreference.

One skilled in the art will recognize that the present teachings can beprovided in various forms in addition to those illustrated. For exampleand with additional reference to FIGS. 6-10, the substrate 40 can beprovided in a variety of different forms. Features of the substratesillustrated in FIGS. 6-10 that are generally similar to features of thesubstrate 40 described above are designated using like referencenumbers, but also include an alphanumeric designator. While thesubstrates of FIGS. 6-10 are illustrated as offset substrates, oneskilled in the art will recognize that they may also be provided innon-offset form.

With initial reference to FIGS. 6A-6C, a substrate 40 a is illustrated.The substrate 40 a generally includes a flange 50 a that is operable tosecure the polymeric cover 42 to the substrate 40 a. The flange 50 a isbetween a first base portion 70 a and a second base portion 72 a. Asillustrated, the first base portion 70 a is below the flange 50 a andthe second base portion 72 a is atop the flange 50 a. Below the firstbase portion 70 a is an anti-rotation layer 74 a having a series of tabs52 a extending therefrom that are operable to prevent the polymericcover 42 from rotating about the substrate 40 a. As illustrated, theanti-rotation layer 74 a has four tabs 52 a. A coupling taper 44 a iswithin the anti-rotation layer 74 a and the first base portion 70 a. Thecoupling taper 44 a is sized to cooperate with the taper adaptor 16. Anaxis A of the coupling taper 44 a is offset from an axis B of thepolymeric cover 42. Further, the anti-rotation layer 74 a is offset fromthe first and the second base portions 70 a and 72 a.

With reference to FIGS. 7A-7C, a substrate 40 b is illustrated. Thesubstrate 40 b generally includes a flange 50 b that is operable tosecure the polymeric cover 42 to the substrate 40 b. As illustrated, theflange 50 b is atop a first base portion 70 b and beneath a second baseportion 72 b. Below the first base portion 70 b is an anti-rotationlayer 74 b with tabs 52 b that are operable to prevent the polymericcover 42 from rotating about the substrate 40 b. A coupling taper 44 bis within anti-rotation layer 74 b and is sized to cooperate with thetaper adaptor 16. An axis A of the coupling taper 44 b and the first andthe second base portions 70 b and 72 b is offset from an axis B of thepolymeric cover 42.

With reference to FIGS. 8A-8C, a substrate 40 c is illustrated. Thesubstrate 40 c generally includes a flange 50 c between a first baseportion 70 c and a second base portion 72 c. Below the first baseportion 70 c is an anti-rotation layer 74 c with tabs 52 c. A couplingtaper 44 c is within the anti-rotation layer 74 c. An axis A of thecoupling taper 44 c is offset from an axis B of the polymeric cover 42.

With reference to FIGS. 9A-9C, a substrate 40 d is illustrated. Thesubstrate 40 d includes a flange 50 d that sits atop a base portion 70d. The flange 50 d is a retention feature that secures the polymericcover 42 to the substrate 40 d. Below the base portion 70 d is ananti-rotation layer 74 d. A coupling taper 44 d is within theanti-rotation layer 74 d. An axis A of the coupling taper 44 d and thebase portion 70 d is offset from an axis B of the polymeric cover 42.

With reference to FIGS. 10A-10C, a substrate 40 e is illustrated. Thesubstrate 40 e generally includes a flange 50 e between a first baseportion 70 e and a second base portion 72 e. Below the first baseportion 70 e is an anti-rotation layer 74 e with tabs 52 e. A couplingtaper 44 e is within the anti-rotation layer 74 e. An axis A of thecoupling taper 44 e and the first and the second base portions 70 e and72 e is offset from an axis B of the polymeric cover 42.

The substrates 40 a-40 e provide a customized head height and shape fordifferent patients. For example, if a lower or flatter head isdesirable, less polymeric material can be used over each of thedifferent substrates 40 a-40 e. Further, each of the first base portions70 a-70 e and/or the second base portions 72 a-72 e can be made thinner.Making the first base portions 70 a-70 e thinner positions the flanges50 a-50 e closer to the respective anti-rotation layers 74 a-74 e.

Conversely, if a higher, or more rounded head is desirable, additionalpolymeric material can be used over each of the different substrates 40a-40 e. Further, each of the first base portions 70 a-70 e and/or thesecond base portions 72 a-72 e can be made with an increased thickness.Increasing the thickness of the first base portions 70 a-70 e positionsthe flanges 50 a-50 e further from the respective anti-rotation layers74 a-74 e. The change in position of the flanges 50 a-50 e can berepresented as changes with respect to any fixed location of thesubstrates 40 a-40 e, such as with respect to the coupling tapers 44a-44 e or any other interface surface.

With exemplary reference to FIGS. 7A-C and 8A-C, the first base portion70 b is thicker or taller than the first base portion 70 c. The distancebetween the flange 50 b and the anti-rotation layer 74 b is greater thanthe distance between the flange 50 c and the anti-rotation layer 74 c.As a result, the polymeric cover 42 of the substrate 40 b is morerounded and is higher than the polymeric cover 42 of the substrate 40 c.Thus, the flanges 50 a-50 e are a first distance from the respectiveanti-rotation layers 74 a-74 e when the polymeric cover 42 has a firstradius of curvature and the flanges 50 a-50 e are a second distance fromthe respective anti-rotation layers 74 a-74 e when the polymeric cover42 has a second radius of curvature. Multiple heads 18 each having adifferent size, shape, and/or radius of curvature can be providedtogether in a kit.

With additional reference to FIG. 11A, an additional substrate accordingto the present teachings is illustrated at reference numeral 40 f.Unlike the other substrates described herein, the substrate 40 f doesnot have a flange to retain the polymeric cover 42. Instead, thesubstrate 40 f includes a knurled surface 76. The knurled surface 76retains the polymeric cover 42, which is molded thereto, and helpsprovide the cover 42 with a uniform thickness.

With additional reference to FIG. 12A, the head 18 can also be madeentirely out of a suitable polymeric material, such as ultra-highmolecular weight polyethylene, polyether ether ketone (“PEEK”), carbonfiber reinforced PEEK (such as PEEK-OPTIMA® from Invibio, Ltd. of theUnited Kingdom), and/or vitamin E stabilized highly crosslinkedpolyethylene (HXLPE) (such as E1™ Antioxidant Infused Technology byBiomet Orthopedics, Inc. of Warsaw, Ind.). A female taper 78 can beformed out of the polymeric material of the head 18, thus making thesubstrate 40 unnecessary. The female taper 78 can be sized and shaped tocooperate with the first male taper 36 of the taper adaptor 16 to createa Morse taper between the taper adaptor 16 and the head 18.

The female taper 78 can be provided in the polymeric head 18 in anysuitable manner. For example, the convex articulating surface 30 can beformed by injection molding and the female taper 78 can subsequently bemachined therein. To support the head 18 as the taper 78 is machinedtherein, support material can be added to the convex articulatingsurface 30 during the molding process. This support material can beremoved after the taper 78 is complete. Alternatively, the taper 78 canbe machined into a blank block of polymeric material having a boss orother support surface by which the block can be held as the taper 78 ismachined therein. The block can be supported at the newly formed taper78 and the convex articulating surface 30 can be subsequently machinedtherein.

One of ordinary skill in the art will recognize that each of the taperlocks described herein can be modified such that the male and femalesides of the tapers are reversed. For example, the female taper 44 fillustrated in FIG. 11A can be a male taper 44 f as illustrated in FIG.11B and the taper adaptor 16 can be provided with a female taper forcooperation therewith. Further, the female taper 78 of FIG. 12A can be amale taper 78 as illustrated in FIG. 12B.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the invention. Individual elements or features ofa particular embodiment are generally not limited to that particularembodiment, but where applicable are interchangeable and can be used ina selected embodiment, even if not specifically shown or described. Thesame may also be varied in many ways. Such variations are not to beregarded as a departure from the invention, and all such modificationsare intended to be included within the scope of the invention.

What is claimed is:
 1. A shoulder implant assembly comprising: a humeralstem configured to be inserted into a humerus bone; a head including: ametal substrate having a coupling taper; and a polymeric cover mountedto the metal substrate having a convex outer surface and a generallyplanar base; a cup having a concave surface configured to articulatewith the polymeric cover of the head; and a taper adaptor configured tomate with the coupling taper of the head, the taper adaptor configuredto connect the head to the stem when the cup is connected to a glenoid,and the taper adaptor configured to connect the head to the glenoid whenthe cup is connected to the humeral stem.
 2. The shoulder implantassembly of claim 1, wherein the coupling taper is configured to createa Morse taper with the taper adaptor.
 3. The shoulder implant assemblyof claim 1, wherein the metal substrate includes a knurled surface forconnecting the polymeric cover to the metal substrate.
 4. The shoulderimplant assembly of claim 1, wherein the metal substrate includesanti-rotation tabs to prevent the polymeric cover from rotating aboutthe metal substrate.
 5. The shoulder implant assembly of claim 1,wherein the metal substrate includes a flange configured to attach thepolymeric cover to the metal substrate.
 6. The shoulder implant assemblyof claim 1, wherein size and shape of the head can be modified bychanging the size of the metal substrate.
 7. The shoulder implantassembly of claim 1, wherein the polymeric cover is injection moldedover the metal substrate.
 8. The shoulder implant assembly of claim 1,where the metal substrate includes at least one of cobalt-chrome andtitanium.
 9. The shoulder implant assembly of claim 1, wherein thepolymeric cover includes at least one of carbon fiber reinforcedpolyether ether ketone and vitamin E stabilized highly crosslinkedpolyethylene.
 10. The shoulder implant assembly of claim 1, wherein thecup includes at least one of carbon fiber reinforced polyether etherketone and vitamin E stabilized highly crosslinked polyethylene.
 11. Theshoulder implant assembly of claim 1, wherein the cup includes at leastone of cobalt-chrome and titanium.
 12. The shoulder implant assembly ofclaim 1, wherein the cup includes a unitary metallic base with anarticulating surface formed therein.
 13. The shoulder implant assemblyof claim 1, wherein the coupling taper of the metal substrate includesan axis that is offset from an axis of the polymeric cover; and whereinthe taper adaptor includes a first male taper configured to mate withthe coupling taper and a second male taper configured to mate with thehumeral stem, the first male taper is offset from the second male taper.14. A shoulder implant assembly comprising: a humeral stem configured tobe inserted into a humerus bone; a polymeric head including: a convexouter surface; a polymeric coupling taper; and a generally planar base;a cup having a concave surface configured to articulate with thepolymeric head; and a taper adaptor configured to mate with thepolymeric coupling taper of the head, the taper adaptor configured toconnect the head to the stem when the cup is connected to a glenoid, andthe taper adaptor configured to connect the head to the glenoid when thecup is connected to the humeral stem.
 15. The shoulder implant assemblyof claim 14, wherein the polymeric coupling taper is machined in thehead.
 16. The shoulder implant assembly of claim 14, wherein thepolymeric head includes at least one of carbon fiber reinforcedpolyether ether ketone and vitamin E stabilized highly crosslinkedpolyethylene.
 17. The shoulder implant assembly of claim 14, wherein thecup includes a unitary metallic base with an articulating surface formedtherein.
 18. The shoulder implant assembly of claim 14, wherein the headis entirely polymeric.
 19. A shoulder implant assembly comprising: ahumeral stem configured to be inserted into a humerus bone; a headincluding a metal substrate and a polymeric cover mounted to the metalsubstrate, the metal substrate including: a first base portion; a secondbase portion; a flange between the first base portion and the secondbase portion, the flange configured to secure the polymeric cover to themetal substrate; an anti-rotation layer on a side of the first baseportion opposite to the flange; a coupling taper defined within theanti-rotation layer; and a plurality of tabs extending radially outwardfrom the anti-rotation layer, the tabs configured to prevent thepolymeric cover from rotating about the substrate; a cup including aunitary metallic base defining a concave articulating surface that isconfigured to articulate with the polymeric cover of the head; and ataper adaptor including a first male taper configured to mate with thecoupling taper of the head and a second male taper configured to matewith the humeral stem, the first male taper is offset from the secondmale taper; wherein a first longitudinal axis extending through a centerof the polymeric cover is parallel to and offset from a secondlongitudinal axis extending through a center of each of the couplingtaper, the first base portion, and the second base portion; and whereinthe polymeric cover is molded over the first base portion, the secondbase portion, and the flange, and is arranged between the tabs.
 20. Theshoulder implant assembly of claim 19, wherein the polymeric coverincludes at least one of carbon fiber reinforced polyether ketone andvitamin E stabilized highly crosslinked polyethylene.